The invention relates to a drive arrangement for a small electrically driven appliance, such as a mincer, a shredder, a pump or a hobby appliance, in which two drive motors drive the work shaft of a load via a common drive wheel.
Small domestic appliances, for example citrus juice extractors, and can openers are driven by two-pole single-phase synchronous motors of compact construction and a high power per volume, typically low of output power on the rotor shaft. When the number of different motor types to be manufactured is limited, the production of these motors can be automated to minimize production cost. However, motors manufactured in mass-production quantities should have a range of output powers suitable for a complete series of appliances.
Doubling of the rotor-shaft power output cannot be achieved by just scaling-up the dimensions to obtain twice the power output. A new production line must be set up, with new or modified machines for manufacturing the laminations, winding the coils etc. Of such a motor can be used only for one specific product in limited quantities and not for a whole range of products, the cost for a new automated production line is not justified.
From EP Patent Application No. 127,050 it is known to drive a kitchen machine with at least two electric motors which cooperate with a common worm wheel via worm shafts. Such worm wheels exhibit a substantial degree of self-braking and thus lead to a low power consumption. If for reasons of power and cost the drive motors are constructed as single-phase synchronous motors, in the case of a high drive shaft load synchronous motors will fail to start. In the case of an arbitrary construction and arrangement of such a multi-motor drive using single-phase synchronous motors, starting of the appliances is difficult and often impossible. The appliance rather performs an irregular movement with much noise and vibrations, or even completely fails to start.